658 NEW YORK STATE MUSEUM 



sequent closing might under the local circumstances have accom- 

 plished, as in existing glaciers, such minor changes of water level.* 

 A glance at the toi)ogra})hic map will show that from Flushing 

 bay, the shore line of which at the time the College Point delta 

 was deposited must have been about 40 feet higher than now, there 

 is a well defined channel extending westward from Newton tlirough 

 Wintield Junction to the head of Newtown creek. From this point 

 escape of the water to or connection with the sea was possible 

 either along the northwestward course of Newtown creek to the 

 East river at Hunters point or, if that way was still blocked by the 

 ice sheet, along a more southerly course between Williamsburg and 

 Brooklyn into Wallabout bay, the highest land there lying between 

 the 20 foot and 40 foot contours. From Wallabout bay a somewhat 

 winding passage below the 40 foot level was open, permitting dis- 

 charge into or connection with Gowanus bay just north of the 

 moraine at the Narrows. 



As for the possibility 

 of the 40 foot delta at 

 N College Point having 



2^LmL -b^ ^^^^^^^^^ *^-^^5^s^%_ been deposited at sea- 



""^^ ^^^- level, it should be 



Fig. 9 CYoss-section of the structures observed in the Col- Stated that similar for- 

 lege Point delta, n, fore-set beds; 6, top set beds; c, , . i r i 



morainal ridge or bar matlOUS UOrtll 01 the 



moraine indicate wide- 

 spread waters at about this level. When these have been fully 

 investigated it may be necessary to admit a submergence to this 

 extent. What is stated here must be taken with this reservation 

 in mind. 



' See, on the formation of tcmporar.v lakes at the present time, Edouard Suess, 

 La face de la terre. Paris. 1900. 2 : 590-97. and the authors there cited; also De 

 Upparent. Traite de peologie. 4me ed. Paris, 1900. p. 302-3, on the sudden 

 drainage of glacial lakes. For American glacial lakes of the class here described, 

 •f<? H. B. KGmraell. Lake Pas.saic. an extinct glacial lake, in N. J. geol. «ur. 

 an. rcp't for 1893. Trenton 1894. p. 225-328; .separately printed 1895. p. 1-89; 

 Crosby and Grabau. Glacial lake deposits near lioston, Science. 1896. 3 : 212- 

 13; also Grabau in Crosby's Geology of the Boston basin. 1900. v. 1. pt 3, 

 p. 564-lK)0, pi. 25; and Warren Upham, The glacial lake Agassiz, U. S. geol. 

 8ur. Monogniph 25. 1895. G58 p. 



